Ronaldo was strongly linked with a move to the Saudi Pro League side after his second spell at Manchester United ended in late November.
Al Nassr emerged as frontrunners and on Friday the 37-year-old’s transfer was officially confirmed. Reports have suggested Ronaldo has signed a two-and-a-half-year deal and will earn £62million (€69.9m) per season.
“History in the making,” Al Nassr tweeted.
“This is a signing that will not only inspire our club to achieve even greater success but inspire our league, our nation and future generations, boys and girls to be the best version of themselves. Welcome @Cristiano to your new home @AlNassrFC.”
Ronaldo’s move is seen as effectively bringing down the curtain on one of the greatest careers in the history of elite European Football.
The five-time Ballon d’Or winner has lifted the Champions League trophy on five occasions — four times with Real Madrid and once with United, while his tally of 140 goals is the highest recorded in Europe’s premier club competition.
Ronaldo is also Madrid’s all-time top scorer with 450 goals, while he became the highest-scoring player in the history of men’s international football last year — he now has 118 senior goals for Portugal.
Al Nassr are coached by former Lyon boss Rudi Garcia and count Cameroon forward Vincent Aboubakar and ex-Arsenal goalkeeper David Ospina among their squad.
The Riyadh-based side have won Saudi Arabia’s top flight on nine occasions — a tally only bettered by Al Hilal, who have 18 titles to their name.